For many years dentistry has enhanced the quality of life of mankind by providing crowns for damaged, decayed or disfigured teeth. When a tooth is partially broken off, is disfigured or has been damaged by decay, a modern dentist can restore the tooth both in function and appearance to a desired external shape by applying a crown. As commonly practiced today, a dentist first takes an impression employing a plastic material of the patient's tooth or teeth. In some cases, an impression will include all of the patient's upper teeth or all of the patient's lower teeth.
From such impression, a model is easily made by filling the impression with plaster or stone that hardens and, after hardening, is easily removable from the soft plastic impression to faithfully replicate a patient's upper or lower teeth, including the adjacent gingival areas. The dentist then prepares the damaged tooth to receive a crown by removing external portions. To do this, the dentist grinds away external parts of the tooth to reduce the total dimensional size of the tooth to be crowned so that all exterior portions thereof are confined within an area less than that of the desired crown. After the tooth has been prepared by removing exterior portions, a second impression is taken from which a second plaster model is made.
These plaster models are then sent to a dental laboratory where a laboratory technician manufactures a crown. After the crown is completed, it is returned to the dentist who then cements or otherwise bonds it in place on the patient's prepared tooth.
This procedure works satisfactorily except that it takes from several days up to several weeks from the time the dentist makes the impressions until the crown is returned to the dentist from the lab for insertion in the patient's mouth. Typically when a tooth is prepared to receive a crown it is very visually distractive, sensitive and vulnerable. To enable a patient to function both physically, that is to masticate food, and to function socially, that is to have a reasonable appearance, the typical procedure is that the dentist forms a temporary crown by molding temporary crown forming material on the prepared tooth and shaping it and hardening it in the patient's mouth so that the temporary crown will last until the permanent crown made by the dental laboratory is returned to the dentist ready for insertion in the patient's mouth.
The crown procedure is for restoration of a single tooth. Restoration of multiple teeth or multiple missing teeth requires dental prostheses. Dental prostheses are divided into two categories, fixed and removable. Fixed prostheses are tooth and/or implant supported bridges that are bonded or cemented into place and are not routinely removed by the patient. Removable prostheses include: partial dentures, complete or full dentures, bite or occlusal appliances, orthodontic appliances, snoring and sleep apnea appliances. Partial dentures are tooth, tissue and/or implant supported and are removable by the patient for routine cleaning and home care. Complete dentures are tissue or implant supported, as the patient has no remaining teeth on the maxilla, mandible, or both. The occlusal, orthodontic, snoring, mouth guard and sleep apnea appliances may be supported by tooth, implant, tissue or a combination thereof.
Temporary and provisional prostheses are not made by the dentist but are generally fabricated by a dental laboratory. The materials available to the lab for their construction often do not hold up well to extended use in the mouth. Restoration for a patient receiving implants may require a provisional restoration to last a year or more, and maintain the vertical dimension of the patient's bite during that time. Partial dentures are problematic in that they require a metal substructure for support. Complete dentures are typically made with a cold curing acrylic resin, which is porous, has residual free monomer, and absorbs odors, stains and bacteria.
Preparing a temporary prosthesis has been a problem in the dental profession for many years. Such temporary prostheses frequently break or dislodge before the patient returns to the dental office to receive the permanent prosthesis. Problems associated with prostheses for the dentist and dental laboratory include the equipment used for making prostheses, which vary greatly between laboratories. The materials used for making them vary as well depending on which equipment a particular dental laboratory uses.
The equipment can be categorized as hot press or cold press. Of the approximately 40,000 dental laboratories currently operating in the U.S., only about 1.5% have access to hot press equipment. It is the hot press equipment, made by companies including Dental D, Pressing, Flexite, Dentsply FRP and Valplast that currently use thermoplastic resins to make temporary, provisional and permanent prostheses. Thermoplastic resins can be used, for example, to make a temporary or provisional fixed bridge, the substructure framework for a partial denture, or the baseplate of a partial or complete denture. Prostheses made from thermoplastic resins look more natural in the patient's mouth and are stronger and less subject to problems such as allergic reactions or damage from porosity.
Not only is the number of dental laboratories with thermoplastic resin capability small, each equipment manufacturer requires special tools for their use. For example, certain existing thermoplastic dental resin systems require the use of a special oven with a disposable aluminum/tin tube or cylinder and/or Teflon plunger to press a thermoplastic dental prosthesis. These ovens are expensive, costing several thousand dollars and the tubes they require to contain the resin are expensive (costing about $2.00 apiece) and can only be used once. The metal tubes may contaminate the thermoplastic resins held inside of the tubes while they are being melted by imparting a gray discoloration to the prostheses. These tubes are also uniquely sized by each manufacturer; so that one manufacturer's thermoplastic material and tubes cannot be used in another manufacturer's oven and injection molding system.
The difficulties and expense in using hot press injection molding equipment for temporary prostheses are solved by the instant invention. The materials and processes described herein allow the use of more aesthetic, stronger, safer and functional thermoplastic resins in temporary prostheses without the use of expensive hot press machines and materials, including special one-use aluminum tubes.
In the past, various patents have issued that deal with materials and methods for making dental prosthesis. For example, in U.S. Pat. No. 5,869,548, Ikushima describes a dental material that is a core ceramic material that is infused with resin to create a block of tooth colored material which is used in a CAD/CAM device to create a dental prosthesis.
In U.S. Pat. No. 5,302,104 Ueda describes a resin denture base molding apparatus which uses acrylic resin for a denture baseplate. The patent is concerned with vertical guide rods and adjustable tables, their container means requires pressure to “break” it. In U.S. Pat. No. 5,635,545, Osman uses various thermoplastic resins which are imprinted with a heat-stable custom shape custom shape memory after it is processed, primarily for making impressions in the mouth.
In U.S. Pat. No. 6,287,490 Rheinberger discloses a method for manufacturing dental prostheses. This patent uses light and pressure to create a polymerizable resin on a model.
In U.S. Pat. No. 6,231,337 Boyd discloses a method of making a dental mouthpiece. This patent uses a light polymerizable resin material to create a mouthguard in the mouth.
In U.S. Pat. No. 5,975,906 Knutson describes a dead-soft polymer dental strip to create a dental prosthesis in the mouth.
In U.S. Pat. No. 6,267,596 Kalfax discloses a dental appliance that uses a resin as a swing lock mechanism to hold a dental appliance in contact with teeth.
The prior art patents that deal with fashioning dental appliances in the patient's mouth do not result in a properly fitted dental prosthesis as does the instant invention. In U.S. Pat. No. 5,302,104 Ueda uses acrylic resin for a denture baseplate that breaks under pressure. The instant invention uses a pre-perforated container that will separate under light pressure. The instant containment means can also be an open ended bag that does not require pressure to rupture or “break” it.
There has not been a patent found or device known that can accomplish the creation of dental prostheses in the low cost, efficient manner accomplished and explained herein by applicants.